The Influence of Parental Factors on the Growth and Metabolism of Children

Abstract

We are currently undergoing the most remarkable shift in human reproductive behaviour since the post-war baby boom. Couples are having children at more advanced ages, leading to an increase in maternal and paternal ages at childbirth. Couples are also choosing to have fewer children, leading to a dramatic increase in the proportion of first-born children in the population. Uptake of fertility treatment is increasing exponentially worldwide, with much attention given to children conceived by assisted reproductive technology (ART). Despite constituting a much larger proportion of the population conceived with fertility treatment, offspring conceived with ovarian stimulation alone (OSA) are remarkably under-researched. The impact of changes in the early fetal environment on offspring phenotype and disease risk is well recognised. Maternal and paternal ages at childbirth, birth order, and OSA fertility treatments all affect the early environment at gametogenesis and/or embryogenesis. We hypothesised that alteration of these environments by parental factors would lead to changes in growth, adiposity, metabolism, and hormonal profiles in childhood. The possible impacts of these parental factors on childhood phenotype have not been previously examined. In my studies of almost 400 children, I found that:  Increasing maternal age at childbirth was associated with taller stature and reduced adiposity in her children, independent of paternal age and birth order.  Similarly, increasing paternal age at childbirth was associated with taller stature and reduced adiposity in children, but with less favourable lipid profiles.  First-born children were taller than second-born children, who were in turn taller than third-borns.  Children conceived with OSA fertility treatment were shorter than naturally conceived children of fertile and subfertile parents. OSA children also had reduced adiposity and displayed subtle metabolic changes compared to those conceived naturally. Thus, my studies demonstrate that a number of parental factors impact on childhood phenotype and disease risk profiles. As a result, the on-going demographic shift in reproductive behaviour is leading to changes in childhood height, adiposity, and metabolism, which may have implications for their future health and disease risk.